Telecommunications networks, such as telephone networks, are subject to failure. Given the volume of traffic and the criticality of some of the traffic on such telecommunications networks, it is desirable to be able to restore from failure as quickly as possible. In general, restoration involves the following steps: (1) detecting the failure; (2) isolating the location of the failure in the network; (3) determining a restoral route for network traffic; and (4) implementing the restoral route.
It is generally desirable to restore a failed network within a few seconds or less. Networks are typically restored by first restoring higher priority network elements and then restoring lower priority elements. Many conventional systems develop a "pre-plan" for restoring networks. These "pre-plans" are developed by simulating possible network failures and determining restoral routes to restore from the simulated failures. The development of these "pre-plans" entails collection of large amounts of data that reflect the logical topologies of the networks. Oftentimes, the data is collected from network engineering databases, which reflect the logical construction of the network by indicating connections and paths of network traffic trunks. A network analyst analyzes the collected data, compares the collected data to the physical topologies and then generates the "pre-plans." Since these "pre-plans" are developed prior to network failure, one of the "pre-plans" is ensured to be available for restoring traffic when a failure occurs. In general, these "pre-plans" are developed for a given segment of a network that can incur a failure. When the segment fails, the corresponding "pre-plan" is utilized.
Unfortunately, such static "pre-plans" have drawbacks. The topology and configuration of a network are frequently subject to change. The "pre-plans" do not account for such changes; rather, the "pre-plans" are developed for a given snapshot (i.e., a fixed topology and configuration) for the network. In addition, events may occur that make parts of the network unavailable so that the "pre-plans" fail because the "pre-plans" presume that the unavailable portions of the network are available.
Another class of restoration approaches dynamically determines restoral routes at the time of failure. Such "dynamic restoration methods" do not suffer the problems of inflexibility that are encountered with the static restoration methods described above. The dynamic restoration methods formulate a restoral route dynamically during the restoration process to use the most accurate and recent data regarding the network that is available. The drawback of such dynamic restoration approaches is that they require extensive and time-consuming analysis during the restoration process. As a result, the restoration process takes longer than with static restoration methods.